kernel-6.6/0607-arm64-stub-fixed-secondary-cores-boot-on-Baikal-M-So.patch

From bd997a1e8e262706b5a65cb1ff48f939c698b835 Mon Sep 17 00:00:00 2001
From: Alexey Sheplyakov <asheplyakov@basealt.ru>
Date: Mon, 23 May 2022 19:28:24 +0400
Subject: [PATCH 607/631] arm64-stub: fixed secondary cores boot on Baikal-M
 SoC

Old versions of Baikal-M firmware (ARM-TF) deny execution attempts
outside of the (physical) address ranges
[0x80000000, 0x8FFFFFFF] and [0xA0000000, 0xBFFFFFFF]
Thus PSCI calls to boot secondary cores fail unless the kernel image
resides in one of these address ranges. However UEFI PE/COFF loader
puts the kernel image into the forbidden range. Since the alignment
is good enough EFI stub does not try to relocate the kernel.
As a result secondary CPUs fail to boot.

Relocation to a random address is not going to work either.
Therefore automatically disable kaslr on "known bad" systems (for
now only Baikal-M) and forcibly relocate the kernel to a low(er)
address.

This patch is necessary only for old firmware (pre SDK-M 5.1) and
prevents kalsr from working on Baikal-M systems.

Signed-off-by: Alexey Sheplyakov <asheplyakov@basealt.ru>
X-DONTUPSTREAM
X-legacy
X-feature-Baikal-M

[ Adapted for kernel 6.6 ]
Signed-off-by: Mikhail Novosyolov <m.novosyolov@rosalinux.ru>
---
 drivers/firmware/efi/libstub/kaslr.c | 61 +++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/efi/libstub/kaslr.c b/drivers/firmware/efi/libstub/kaslr.c
index 1a9808012abd..bbbf496853cd 100644
--- a/drivers/firmware/efi/libstub/kaslr.c
+++ b/drivers/firmware/efi/libstub/kaslr.c
@@ -4,9 +4,47 @@
  * architectures to deal with physical address space randomization.
  */
 #include <linux/efi.h>
+#include <linux/libfdt.h>
 
 #include "efistub.h"
 
+static inline efi_status_t efi_low_alloc(unsigned long size, unsigned long align,
+					 unsigned long *addr)
+{
+	/*
+	 * Don't allocate at 0x0. It will confuse code that
+	 * checks pointers against NULL. Skip the first 8
+	 * bytes so we start at a nice even number.
+	 */
+	return efi_low_alloc_above(size, align, addr, 0x8);
+}
+
+static const char* machines_need_low_alloc[] = {
+	"baikal,baikal-m",
+	"baikal,bm1000",
+};
+
+static bool need_low_alloc(void) {
+	size_t i;
+	const void *fdt;
+	const char *match;
+
+	fdt = get_efi_config_table(DEVICE_TREE_GUID);
+	if (!fdt) {
+		efi_info("failed to retrive FDT from EFI\n");
+		return false;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(machines_need_low_alloc); i++) {
+		match = machines_need_low_alloc[i];
+		if (fdt_node_check_compatible(fdt, 0, match) == 0) {
+			efi_info("machine %s: forcing kernel relocation to low address\n", match);
+			return true;
+		}
+	}
+	return false;
+}
+
 /**
  * efi_kaslr_get_phys_seed() - Get random seed for physical kernel KASLR
  * @image_handle:	Handle to the image
@@ -26,8 +64,17 @@ u32 efi_kaslr_get_phys_seed(efi_handle_t image_handle)
 	if (!IS_ENABLED(CONFIG_RANDOMIZE_BASE))
 		return 0;
 
+	bool force_low_reloc = need_low_alloc();
+	if (force_low_reloc) {
+		if (!efi_nokaslr) {
+			efi_info("booting on a broken firmware, KASLR will be disabled\n");
+			efi_nokaslr = true;
+		}
+	}
+
 	if (efi_nokaslr) {
-		efi_info("KASLR disabled on kernel command line\n");
+		if (!force_low_reloc)
+			efi_info("KASLR disabled on kernel command line\n");
 	} else if (efi_bs_call(handle_protocol, image_handle,
 			       &li_fixed_proto, &p) == EFI_SUCCESS) {
 		efi_info("Image placement fixed by loader\n");
@@ -126,6 +173,15 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
 		status = EFI_OUT_OF_RESOURCES;
 	}
 
+	if (force_low_reloc) {
+		status = efi_low_alloc(*reserve_size,
+				       min_kimg_align,
+				       reserve_addr);
+		if (status != EFI_SUCCESS) {
+			efi_err("Failed to relocate kernel, expect secondary CPUs boot failure\n");
+		}
+	}
+
 	if (status != EFI_SUCCESS) {
 		if (!check_image_region(*image_addr, kernel_memsize)) {
 			efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");
@@ -152,6 +208,9 @@ efi_status_t efi_kaslr_relocate_kernel(unsigned long *image_addr,
 
 	memcpy((void *)*reserve_addr, (void *)*image_addr, kernel_size);
 	*image_addr = *reserve_addr;
+	if (efi_nokaslr) {
+		efi_info("relocating kernel to 0x%lx\n", *image_addr);
+	}
 	efi_icache_sync(*image_addr, *image_addr + kernel_codesize);
 	efi_remap_image(*image_addr, *reserve_size, kernel_codesize);
 
-- 
2.40.1